This application is related to an application entitled Piezoelectric Transducer Drive having the same inventor, the same assignee and the same filing date as the present application.
The present invention relates to the control of the voltage applied to a piezoelectric transducer. The present invention is described in terms of a specific application to path length control in a ring laser gyroscope, however, there are many applications of the present invention that are unrelated to ring laser gyroscopes.
Ring laser angular rate sensors sometimes referred to as ring laser gyros or RLGS are well known in the art. RLGS include a ring laser supported in a block having a plurality of gas containing tunnels. At the intersection of the tunnels are mirrors to define a closed loop optical path which is traveled by the counter propagating laser beams. RLGS typically include a path length controller which has the purpose of maintaining a path length which is equal to an integral number of wavelengths. The path length controller function is usually provided by one of the mirrors being attached to a piezoelectric transducer which controls translational movement of the mirror to affect the laser beam path length. One technique for maintaining path length is detecting the intensity of the laser beams, for example by using a photodiode, and controlling the path length of the RLG such that the intensity as measured by the photodiode is at a maximum.
Various approaches to the electronics for path length control have been utilized. These approaches have ranged from the use of analog signals only for path length control to various Processor in the loop (PITL) path length control approaches. PITL approaches have been proposed for certain PLC signal processing with digital to analog converters and analog amplifiers still used to drive the piezoelectric transducers. The quality of digital to analog converters required for military and certain other applications results in very costly digital to analog devices. Thus a need exists in some PITL applications of RLG path length control to be able to drive the piezoelectric transducer without having to provide the digital to analog converter. Also, there is a need for all digital piezoelectric drive apparatus in applications unrelated to RLGS.